There is a general desire for engines capable of being used for multiple purposes (e.g. in multi-function systems). There is a general desire to extract power from such engines which power may be able to be used to power other devices and to manage the loads in systems incorporating such engines. For example, Miller Electric Manufacturing Co. of Appleton Wis. provides multi-function systems equipped with diesel engines under the brand-name ENPAK™. Such engines may be used to provide power for an electrical generator, an air compressor and a hydraulic pump which are provided integrally with the multi-function system. The hydraulic pump of the ENPAK™ multi-function system is sold as a part of the multi-function system itself and comprises a variable displacement hydraulic pump where the pump displacement is varied based on pressure feedback.
A drawback with variable displacement hydraulic pumps is that their components are relatively more sensitive (e.g. less robust) and more complex (e.g. to control) in comparison to fixed displacement hydraulic pumps. Further, variable displacement pumps are generally more expensive than fixed displacement hydraulic pumps. Some users may not need variable displacement hydraulic pumps. Some users may want to provide their own hydraulic pump which may be suited to their particular needs. Some users may want to change hydraulic pumps from time to time. Some users may also want to vary the type of accessory devices in a multi-function system. For example, some users may want to have a multi-function system with a drive shaft output which may provide mechanical power to some other accessory device such as a water pump, an auger and/or the like. As another example, some users may want switch from time to time between a hydraulic pump and a drive shaft output which provides mechanical power to some other accessory device such as a water pump, an auger and/or the like.
There is a general desire to provide engines with power take-offs (also referred to as PTOs or power take-off ports) for extracting power from the engines for use to power other devices. By way of non-limiting example, such other devices may include hydraulic pumps and/or the like. There is a general desire to permit users to be able to relatively easily connect and disconnect their own devices to such power take-offs.
Emissions standards for off-highway engines have been getting relatively stricter, particularly for off-highway engines having greater than specified power outputs. By way of non-limiting example, in the case of diesel off-highway engines, the United States Environmental Protection Agency (EPA) and similar standards bodies in other countries have adopted the Tier 4 standard for diesel off-highway engines. These emissions standards are easier to meet for relatively small power engines (e.g. engines under 25 horsepower (19 kW) have emissions standards that are relatively less strict than engines over 25 hp (19 kW)). For example, engines under 25 hp (19 kW) require NMHC+NOx emissions of less than 7.5 g/kW-hr (a standard that has not changed since 2005), whereas engines having the next higher classification (19 kW-37 kW) require NMHC+NOx emissions of less than 4.7 g/kW-hr (a standard that has decreased as of 2013). Accordingly, there is a general desire to provide off-highway engines having relatively low power outputs (e.g. less than 25 hp (19 kW) or less than some other suitable power threshold). At the same time, however, there is a competing desire to maximize the power output available at power take-offs to thereby provide maximum versatility to the types of devices that can be coupled to such power take-offs and the types of applications for which such devices can be used.
There is a general desire to manage the loads for multi-function systems incorporating power take-offs and used to provide power to a number of different accessories. By way of non-limiting example, such load management can be used to mitigate against engine overloading, engine wear, to attempt to achieve optimum performance of accessory devices, to mitigate against accessory damage and accessory wear and/or the like.
The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.